Monitoring apparatus and devices are widely used for remotely monitoring a particular parameter or group of parameters. Such apparatus and devices provide reports on such parameters to a central computer system (CCS) equipped with what has come to be known as a personal computer (PC). The apparatus may be configured to provide such reports on a time basis, e.g., and/or upon the occurrence of a predetermined parameter value. Examples of such parameters include liquid flow rate, the signal strength of a transmitted radio-frequency signal, temperature, pressure and a host of other parameters relating to process control.
Certain known types of monitoring systems are embodied as a group of automatic dialers with synthesized voice or data telemetry dialers. Such systems "talk to" responding humans or a CCS using the several individual monitoring apparatus or "out stations" or remote terminal units (RTU) as they are sometimes called. Each of such apparatus is coupled to the conventional telephones or CCS by a dedicated conductor or, more typically, by a dial-up telephone line using a standard modem.
Typical monitoring apparatus provide such reports in a digital code which is compatible with the CCS but not with a facsimile machine to which it may transmit data. Therefore, a code conversion is required to be made in the latter instance in order to complete the communication "link" between the apparatus and the facsimile machine. Heretofore, such code conversions have been made using "PC-like" conversion techniques and devices such as floppy discs (with accompanying disc readers). Conversions are also made using specially constructed "program cards," i.e., printed circuit boards insertable into a PC, either arrangement being for the purpose of "loading" conversion programs into and out of memory.
The arrangement shown in U.S. Pat. No. 3,558,811 (Montevecchio et al.) involves an interface adapter unit for converting facsimile signals to computer signals and vice versa. The resulting "hard" or paper copy is under the control of the computer. The Montevecchio et al. arrangement uses selected programs "loaded" to a memory unit and video or video-like signals during the conversion process.
Another, similar system is shown and described in U.S. Pat. No. 4,816,911 (Kirsch et al.). The system shown therein permits communication between a PC and a facsimile machine. The PC is equipped with a communication card and its hard-disc memory may be supplemented by a video card.
Yet another type of monitoring apparatus is described in a brochure relating to what is called the DAMAR.RTM. ("Data Acquisition Monitoring and Reporting System") system, such brochure being published by Sygnus Controls, Inc. The Sygnus system accepts analog process input signals in the 4-20 ma. range, each such signal being directed to a separate plug-in input card which are understood to use PC-like code conversion techniques as aforementioned. There is no apparent provision for accepting digital input signals. Both time-based and event-based reports are generated and sent to a facsimile machine and archival data storage can be accomplished with an optional floppy disc drive.
The apparatus and systems described in the foregoing patents and Sygnus brochure tend to share certain disadvantages. A major disadvantage is that such systems use a PC or PC-like techniques and hardware to convert code from the monitoring apparatus into a code compatible with a facsimile machine. The Sygnus apparatus additionally requires conversion of analog signals into digital code before any digital code conversion can occur. Another disadvantage of the Sygnus apparatus is that it is apparently unable to communicate with a CCS. Irrespective of the particular type of system, code conversion using PC-like techniques adds materially to its cost and complexity.
A monitoring apparatus which has a conversion code embedded in firmware to convert text data in a first code (such as ASCII) into a second code (such as scan line code used by facsimile machine) would be an important advance in the art. Such an apparatus could be directly interposed between a measuring device such as a pressure gauge and a facsimile machine (and, optionally, a PC), thereby negating any need for the aforementioned PC or PC-like conversion techniques with their attendant cost. A related method for transmitting a report in binary text data from a monitoring apparatus directly to a facsimile machine would likewise be an important advance in the art.